1. Field of Art
This invention is addressed to closures for sealing containers and in particular to a plastic closure having an integral sealing means therein.
2. Brief Description of the Prior Art
It is well-known to provide plastic closures having integral sealing means which obviate the need for a separate sealing liner or gasket in the closures. Elimination of a separate liner or gasket reduces the cost of closures. Linerless closures frequently have depending annular fins or ribs which seal against the container finish as disclosed in U.S. Pat. Nos. 3,224,617 and 3,844,439. Other linerless closures include deflectable diaphragm portions for sealing against the container surface as disclosed in U.S. Pat. Nos. 2,914,206; 3,160,303 and 3,414,151.
Among the disadvantages of prior art linerless plastic closures are poor sealing capabilities on rough or wavy container finishes and limited shelf life due to stress relief of the plastic during aging with resultant loss of sealing. Sealed containers should have a one-year shelf life without loss of the seal.
An improved linerless plastic closure is desired which will overcome the disadvantages of the prior art closures.